Make sure you're using proper date formatting for filenames with dates and any date values in the YAML front matter of your files. Dates must be formatted as YYYY-MM-DD HH:MM:SS for UTC, and must be actual calendar dates.

If you specify a date format in your _config.yml file, make sure you format it correctly. To specify a time zone with an offset from UTC, use the format YYYY-MM-DD HH:MM:SS +/-TTTT. For example: 2014-04-18 11:30:00 +0800.

Once you've fixed all post date errors, you will need to commit your changes and push to your GitHub Pages repository again to trigger another build on the server.